Isomerization of saturated hydrocarbons



. l, 1959 v. HAENSEL IsoMERIzATIoN 0F SATURATED HYDRocARBoNs Filed Nov. 13. 19,57

N V E N TOR.- V/ad/'m/r Haense/ fm y @mja ATTORNEYS.

United States Patent O ISOMERIZATION OF SATURATED HYDROCARBONS Application November 13, 1957, Serial No. 696,241

20 Claims. (Cl. Mtl-683.68)

This invention relates to the isomerization of saturated hydrocarbons in the presence of an isomerization catalyst. More particularly, this invention relates to the isomerization of paraflinic and cycloparanic hydrocarbons in a unitary process comprising selective fractionation, isomerization, ring opening, and recycle. Still more particularly, this invention relates to the vapor phase isom erization of paraftnic and cycloparaflinic hydrocarbons boiling above butanes and'pentanes in which process high yields of high antiknock hydrocarbon fractions are produced with minimum loss to byproducts such as dry gas and high boiling materials. Simultaneously with the maximum utilization of available relatively straight chain paraflinic hydrocarbons and naphthenic hydrocarbons, this invention relates to a particular series of process steps, the use of which results in maximum catalyst life and optimum product quality. This invention is particularly directed to an improved process for the production of high octane number hexane hydrocarbons by the isomerization of relatively straight chain hexane hydrocarbons and by ring opening of methylcyclopentane. These objectives are accomplished by the unique combination process of the present invention as will be set for-th hereinafter.

Production of highly branched chain paralinic hydrocarbons having high antiknock properties and therefore suitable for use in automotive and aviation fuels is of considerable importance in the petroleum refining industry. Furthermore, the recent introduction of automobile engines of high compression ratio has necessitated the ,utilization of high antiknock fuels in these engines to obtain maximum horsepower output therefrom. Thus, the demand for higher and higher octane number fuels has led to the need for increased quantities of highly branched chain paranic hydrocarbons for use as blending agents in gasoline. A convenient source of highly branched chain parainic hydrocarbons is the products from the catalytic isomerization of less highly branched chain parainic hydrocarbons. Normal butane nad normal pentane have been isomerized to isobutane and isopentane respectively by prior art processes utilizing either liquid or vapor phase. However, it is well known in the art that cracking occurs along with isomerization, and that this cracking increases with increasing molecular weight of the hydrocarbon reactants. A process for hexane isomerization is particularly attractive when it is realized that a hexane fraction can be converted by proper isomerization into a motor fuel having an F-l-l-S cc. octane number of over 95. It is therefore an object of this invention to provide a process which will yield these Idesired high octane number hexane isomers.

Prior art processes for the isomerization of saturated hydrocarbons have taught the utilization of various catalytic agents to accelerate Ithe desired molecular rearrangement at the conditions selected. Ordinarily, the catalytic agents utilized have been metal halides such as aluminum chloride, aluminum bromide, etc., which were activated ICC by the addition of the respective hydrogen halide thereto. These catalytic agents are very active and effect high conversions per pass. However, this high activity is accompanied by many disadvantages. One of the greatest disadvantages is the fact that these catalytic materials not only accelerate isomerization reactions, but they also induce decomposition reactions. These decomposition reactions are particularly detrimental to the overall eco nomics of an isomerization process since they cause a loss of a portion of the charging stock as well as increasing catalyst consumption by reaction of fragmental materials with the catalytic agent to form sludge-like materials. In the case of hexane hydrocarbon fractions and those of higher molecular weight, as stated hereinabove, this problern is acute. The process of the present invention overcomes these disadvantages by utilization of more recently developed catalysts and thus the use of the process of the present invention along with these catalysts results in the attainment of isomerization reactions which have hereinbefore been unavailable to the petroleum industry.

However, even the use of more recently developed catalysts does not in itself result in processes which can be utilized for the successful isomerization of hexane hydrocarbon fractions and hydrocarbon fractions of increased molecular weight. This is due to the inherent composition of these fractions. While these fractions are saturated in the sense that they do not contain olens, they contain, in addition to parain hydrocarbons, naphthenes and small amounts of aromatics. The presence of these cyclic hydrocarbons along with the paratfns results in inability to make a separation of one from another by ordinary fractional distillation means. Not only are the boiling points of the various components of such fractions very close together but azeotroping of one with another occurs. For example, hexane fractions contain dimethylbutanes, monomethylpentanes, normal hexane, methylcyclopentane, cyclohexane and some benzene. The dimethylbutanes and the monomethylpentanes can be successfully fractionated from normal hexane and higher boiling hexane hydrocarbons. However, the boiling points of normal hexane and methylcyclopentane are so close to one another that fractionation becomes an ineicient means for separating these components. Since it is always desirous to recycle normal hexane to extinction, the cyclics content of a combined feed in a recycle process tends lto build up to higher and higher quantities if means for the removal of such cyclics are not provided. This increase in quantity of cyclics in the combined feed, after the passage of a sufficient period of time, will result in either complete shutdown of the process or backing out fresh feed from the reactor to an extent which Will also result in eventual shutdown of the process. Furthermore, cyclic or naphthenic hydrocarbons tend to be adsorbed `on a catalyst surface in preference to paraftnic hydrocarbons. Large quantities of cyclic or naphthenic hydrocarbons in isomerization process feed stocks tend to result in diminished conversions of paraffinic hydrocarbons. vantageous to provide a process wherein the quantity of cyclic or naphthenic hydrocarbons in the combined feed to such a process is minimized. By means of the process of the present invention wherein the naphthenic rings of alkylcycloparaftins are opened in a second reaction zone this objective of the present invention can be accomplished.

The process of the present invention is particularly directedto the isomerization of hexane hydrocarbons. Hexane hydrocarbons -boil from about 40 C. to about C. (104-185 F.) and analyses of typical hexane fractions show that they contain varying quantities of cyclopentane, 2,2 dimethylbutane, 2,3-dimethylbutane,

Therefore, it becomes doubly ad-4 Z-methylpentane, S-methylpentane, normal hexane, methylcyclopentane, dimethylpentanes, cyclohexane, and benzene. The boiling points and octane number of these six carbon atom hydrocarbons are given in the following table:

TABLE I Boiling Point F1 Octane No.

C. F. Clear +3 cc.

2,2dimethylbutane 49. 7 121. 5 92. 3 104. 0 2,3-din1ethylbutane- 58. 0 136. 4 103. 5 120 2-methylpentane. 60. 3 140. 5 73. 4 93. 1 3 methylpentane... 63. 3 145. 9 74. 5 03. 4 n-hexane 68. 7 155. 7 25. 0 05. 3 methyleyclopentane. 71. 8 161. 3 92. 0 103. 1 benzene 80, 1 176. 2 120 120 cyclohexane 80. 7 177. 3 84. 0 97. 4

By the process of the present invention the high octane number parainic components are removed from the process and the quantity of naphthenes in the combined feed to the process is reduced by passage of the recycle over an alkylcycloparain ring-opening catalyst prior to combination thereof with the net fresh feed to the isomerization reaction zone. The isomerization reaction zone feed Will then be converted into an equilibrium mixture of parainic and cycloparafnic hexane isomers. In-this manner a total hexane'product is produced having an F-l-l-S cc. octane number of greater than 95.

In one embodiment the present relates to a process for the isomerization of an isomerizable saturated hydrocarbon fraction characterized by an average molecular weight greater than about 80, said isomerization being carried out in the presence of an isomerization catalyst, which comprises passing said hydrocarbon fraction to a first fractionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylparaftins and a bottoms fraction rich in monomethyl, normal, and cycloparafns, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described to an isomerization reaction zone containing an isomerization catalyst and therein isomerizing at isomerization conditions said fraction and recycle to a mixture of isomers thereof, passing the isomerization zone effluent to a second fractionation zone, fractionating said effluent in said zone to produce an overhead fraction rich in dimethyland monomethylparains and a bottoms fraction rich in normal, and cycloparains, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparafn ring-opening catalyst and therein opening the rings of alkylcycloparaftins in the feed to` said zone, and passing the effluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

Ar more specific embodiment of the present invention relates to a process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising a platinum group metal and a refractory metal oxide which comprises passing said hydrocarbon' fraction to a first fractionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich 1n monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottomsv fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reactron'zone containing said isomerization catalyst and therein isomerizing at isomerization conditions in the presence. of? hydrogen said fraction and recycle to a mixture of isomers thereof, passing the isomerization zone 4 eiuent to a second fractionation zone, fractionating said effluent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparafn ring-opening catalyst comprising an iron group metal and therein opening the ring of the methylcyclopentane in the feed to said zone by means of hydrogen, and passing the effluent from said second reaction zone to the isomerization reaction Zone as aforesaid as recycle therefor. A specific embodiment of the present invention relates to a process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina and from about 0.01% to about 2% by weight thereof of platinum, which comprises passing said hydrocarbon fraction to a first fractionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing saidv overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 300 F. to about 825 F., a pressure of from about 100 to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 01 to about 10, passing the isomerization zone effluent to a second fractionation zone, fractionating said effluent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes, and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparafin ring-opening catalyst comprising metallic nickel and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, and passing the eluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

Another specific embodiment of the present invention relates to a process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina, from about 0.01% to about 2% by weight thereof of platinum, and from about 0.1% to about 8% by weight thereof of combined halogen, which comprises passing said hydrocarbon fraction to a rst fractionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with. recycle produced as hereinafter described and hydrogen to anv isomerization reaction Zone containing an isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 300 F. to about 825 F., a pressure of from about 100 to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, passing the isomerization zone efuent to a second fractionation zone, fractionating said' efuent in said` zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparatiin ring-opening catalyst comprising metallic nickel and therein opening the ring of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, and passing the eluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

A further specific embodiment of the present invention relates to a process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina andy from about 0.01 to about 2% by weight thereof of platinum having impregnated thereon from about 2% to'about by weight thereof of a Friedel-Crafts metal halide, which comprises passing said hydrocarbon fraction to a first fractionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 300 F. to about 500 F., `a pressure of from about 100 to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, passing the isomerization zone efuent to a second fractionation zone, fractionating said eluent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpcntanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparaiiin ring-opening catalyst comprising metallic nickel and therein opening the ring of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about to about 2000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, and passing the efuent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor. t l

A still further specific embodiment of the present invention relates to a process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina, from about 0.01% to about 2% by weight thereof of platinum, and from about 0.1% to about 8% by weight thereof of combined halogen, having impregnated thereon from. about 2% to about 20% by weight of a Friedel-Crafts metal halide, which comprises passing said hydrocarbon fraction to a first fractionationyzone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 300 F. to'about 500 F., a pressure of from about to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, passing the isomerization zone eluent to a second fractionation zone, fractionating said euent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction lich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the'second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparafln ring-opening catalyst comprising metallic nickel and therein opening the ring of methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, and passing the efuent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

The combination process of the present invention has diverse advantages, all interrelated. The process prevents a buildup of heavier products in the combined feed to the reaction zone by passage of what would ordinarily be recycled through a second reaction zone containing an alkylcycloparaffin ring-opening catalyst. In this second reaction zone, the catalyst therein performs two distinct functions. The rst of these is the ring opening of the alkylcycloparains in the feed thereto.V In the isomerization reaction zone the naphthenic hydrocarbons in the feed thereto are isomerized to an equilibrium mixture thereof. Therefore, the isomerization reaction zone effluent will always contain alkylcycloparafns in quantities up to those predicted by thermodynamic equilibrium. The process conditions are adjusted so that the quantity of alkylcycloparains produced in the isomeri- Zation reaction zone and present in the effluent therefrom will be equal to the total cyclics content of the net fresh feed. In this manner of operation, there will always be sufficient destruction of cyclics in the alkylcycloparaifin ring-opening reaction zone to maintain the process in cyclics balance. Furthermore, the alkylcycloparaiiin ring-opening catalyst has a second function, that is, as acting as a demethylation catalyst for heavier products which may be produced in the process. Thus, when processing hexanes, the small quantities of heptanes, octanes, etc., which are produced as byproducts, will be demethylated in the second reaction zone thus preventing a buildup of higher boiling reaction products in the combined feed to the isomerization reaction zone. T he process of the present invention has another advantage in that the total quantity of naphthenes which is passed to the isomerization reaction zone is minimized. Cyclic hydrocarbons are more strongly adsorbed on a catalyst surface than are paraflinic hydrocarbons. When the, quantity of cyclic parains increases relative to the quantity of paraifnic hydrocarbons in the feed stock to an isomerization reaction zone, isomerization of the paraftinic hydrocarbons is` repressed. This does not occur in. the process of the present invention, in which process the naphthene content of the combined feed is maintained at a constant value by destruction of alkylcycloparains in-an amount equal to that of the cyclic hydrocarbons content in the net fresh feed. By having a definite quantity of cyclic hydrocarbons in the combined feed to the isomerization reaction zone, cracking of paraiiinic hydrocarbons due to the action of the catalyst is repressed. This is` particularly advantageous in the case of more recently developed catalysts which reach maximum catalytic eiciency in the presence of added hydrogen. With hydrogen and these catalysts, hydrocracking may prevent processingof parafinic hydrocarbons due to excessive amounts of hydrocracking. By maintaining a denite cyclics hydrocarbon content in the combined feed while preventing cyclics hydrocarbon build-up at the same time,

'7 these hydrocracking reactions are minimized and the efficiency of the total reaction based upon the quantity of high octane number isoparafns produced is extremely high. The process of the present invention also prevents so-called reverse isomerization of dimethylparains to monomethylparaffins and normal paraflins by removal of these high octane number components of the fresh feed in a first fractionation zone. Thus, the overall octane number of the process product is substantially increased by allowing further quantities of dimethylparafiins to be formed in the reaction zone from lower octane number monomethylparafins and normal paraffins. It is therefore obvious that the total quantity of high octane number dimethylparaflins produced will exceed that which is fixed by thermodynamic equilibrium for the total fresh feed to the process. Furthermore, the ring opening of the alkylcycloparafiins in the second reaction zone produces a recycle which in addition to containing normal parafns and cycloparaffns, also contains monomethylparaflins which are produced by the ring opening reaction. These monomethylparains are therefore afforded an opportunity to be converted into higher octane number dimethylparans by combination thereof with the fresh feed to the isomerization reaction zone. Another advantage of the process of the present invention is that catalyst deactivation or destruction is minimized or substantially eliminated lby distillation drying of the reactor feed and rejection of small quantities of water contained therein along with the dimethylparafins in the overhead from the first fractionation zone. Thus, the reaction zone feed is a fractionation zone bottoms product and by this means full advantage is taken is undesired and such uncontrolled hydrogen chloride production is substantially eliminated by the present process. By elimination of dimethylparafns from the reaction zone feed, ythe quantity of feed is reduced as well as the combined feedratio and thus the total investment necessary for catalyst can be substantially reduced. These and other advantages will be explained more fully inthe following detailed description of the process of the present invention.

As set forth hereinabove, this invention relates to a process for the production of high antiknock hydrocarbon fractions one step of which includes the isomerization of an isomerizable saturated hydrocarbon fraction characterized by an average molecular weight greater than, about 80. Hydrocarbons within the scope of the above limitation and utilizable in the process of this invention include methylcyclopentane, cyclohexane, normal hexane, Z-methylpentane, 3-methylpentane, Z-methylhexane, 3-methylhexane, S-ethylpentane, normal heptane, methylcyclohexane, ethylcyclohexane, normal octane, 2-methylheptane, 3-methylheptane, etc, As stated previously, the process of the invention is particularly applicable to the isomerization of hexane hydrocarbon fractions. These hexane fractions may be obtained from various sources including fractionation from straight-run gasoline, straight-run naphtha, natural gasoline, catalytically reformed naphtha, and catalytically reformed gasoline. Such hexane hydrocarbon fractions are free from or substantially free from olefin hydrocarbons as is obvious from their source. Analyses of typical hexane fractions from various crude sources are given in the following Table II:

TABLE II Analyses of typical C5 Fractions Fractonation cut -74 C. (104-]65 F.)

Barninus Pennsyl South Gulf Nat'l Natl Composition, Vol. Percent Crude Vania Louisiana Coast Oklahoma Wyoming Arabian Gasol Gasol Texas Texas Cyclopentaue 5 2 2 3 3 4 2 2 5 2,2-Dimethylbutane... Tr 3 2 3 1 1 1 2 3 2,3-Dimethylbutane 5 5 5 5 2 3 3 4 6 2-Methylpentane 20 27 25 25 22 22 22 28 23 3-Metl1ylpei1tane. 19 l'i 18 20 15 14 16 17 15 n-Hexaue 32 36 31 30 40 35 44 34 23 Mcthylcyclopentane 16 6 14 3 14 18 7 9 14 Dmethylpentanes Tr Tr 1 1 1 i Tr Tr Cyelohexane. 1 Tr 1 7 1 1 2 1 2 Benzene 2 2 1 3 2 1 2 3 4 Total 100 100 100 100 100 100 l0() 100 10U C@ Cyclics, Percent 19 8 16 13 7 20 11 13 20 Octane No. F-l-I-S cc 88 86 (88) 90 (85) 86 82 86 92 of maximum distillation drying. All isomerization catalysts depend upon an acid function either alone or in combination with other catalytic functions to accomplish the desired isomerization reaction. This acid function is destroyed or decreased by contact with water. The preferred catalysts of the present invention which operate at elevated temperatures contain this acid function, in small quantities. Thus, small amounts of water, which can be brought in with the feed stock, cause relatively rapid catalyst deactivation. Furthermore, in one specific embodiment of thel present invention, a Friedel- Crafts metal halide such as aluminum chloride is impregnated on and forms an integral part of the isomerization reaction zone catalyst. Reaction of water with aluminum chloride, for example, produces hydrogen chloride, a well known activator for aluminum chloride as an isomerization catalyst. Hydrogen halides such as hydrogen chloride can be utilized along with the catalysts of the present invention. However, their utilization must beV controlled. Uncontrolled production of hydrogen chloride by reaction of aluminum chloride with water A detailed description of the processing of one of these hexane hydrocarbon fractions by the process of the present invention will be given hereinafter.

Various isomerization catalysts are utilizable within the generally broad scope of the process of the present invention. These catalysts are utilized in the isomerization reaction zone described hereinafter. These catalysts include a support, an acid-acting function, and a hydrogenation component. diverse refractory oxides including silica, alumina, titania, boria, zirconia, silica-alumina, silica-alumina-magnesia, silica-alumina-zirconia, silica-zirconia, etc. Depending on the method of preparation and upon the treatment of the support thereafter, these various supports will have surface areas ranging from about 25 to about 500 square meters per gram. In some of these supports the acid-acting function is inherently present, as when silicaalumina is used as the support. The effectiveness of this acid-acting function is then controlled by the quantity of silica which is combined with the alumina, and by the treatment of the silica-alumina, particularly by calcina- The support may be selected fromy tion, prior to or after compositing the hydrogenation component therewith. Of the various supports, alumina is preferred, and particularly gamma-alumina having a surface area of from about 150 to about 450 square meters per gram. When gamma-alumina is utilized as the support, the acid-acting function can be added thereto initially by the incorporation therein of what is known in the art as combined halogen. The amount of cornbined halogen can be varied from about 0.01% to about 8% by weight based on the alumina. Of the various halogens which can be utilized, chlorine and fluorine are preferred, and mixtures of both chlorine and fluorine can be utilized satisfactorily. Thus, in an alumina type catalyst to be utilized at reaction temperatures of from about 750 F. to about 825 F., about 0.3% by weight of uorine and about 0.4% by weight of chlorine may be incorporated in the alumina. When it is desirable to utilize the isomerization process at a lower temperature, for example, one within the range of from about 500 F. to about 750 F., the combined halogen which will be utilized along with the support is uorine, and this uorine may be utilized in an amount of from about 2.5% to about 4.5%.

The catalyst composite Will then have the desired hydrogenation component combined therewith. This hydrogenation component will normally be selected Vfrom the group of metals known as the platinum group. Such platinum group metals include platinum, palladium, ruthenium, rhodium, osmium, and iridium. Of the various platinum group metals which may be utilized, platinum, palladium and ruthenium are preferred, and of these platinum group metals, platinum itself is particularly preferred. The platinum group metal component of the catalyst will normally be utilized in an amount of from about 0.01% to about 2% by weight based on the Weight of the support. Thus, when the platinum group metal is the preferred platinum, the quantity utilized will range from about 0.01% to about 2% by weight. A particularly preferred catalyst comprising platinum, combined halogen, and alumina, will contain about 0.4% platinum, about 4% uorine, andthe remainder gamma-alumina. Because of equilibrium considerations and because it is often desirable and/or advisable to carry out the isomerization reaction at the lowest possible temperature, for example, from about-300 F. to about 500 F., catalysts may also be prepared by impregnating composites such as described hereinabove, either with or withoutcombined halogen, with a Friedel-Crafts metal halide. For example, an excellent low temperature isomerization catalyst can be prepared by impregnating from about 2% to about 20% aluminum chloride onto a composite of platinum and alumina which may or may not contain combined halogen.

The isomerization process of the present invention may be carried out at varying conditions of temperature, pressure, space velocity and combined feed ratio. The temperature utilized will generally be dictated by the particular catalyst selected. Thus, the temperature may range over a Wide range of from about 300 F. to about 825 F. The pressure will range from about 100 to about 1000 pounds per square inch or more. Liquid hourly space velocity in the isomerization reaction zone will range from about 0.1 to about or more, the only limitation being that equilibrium mixtures of isomerized hydrocarbons or a close approach thereto shall be obtained in the effluent from the isomerization reaction zone. The combined feed ratio which is defined as the total amount of fresh feed entering the reactor and recycle divided by the quantity of fresh feed will range from just over one up to about 1.5. Values 'in between these two limitations are determined by thermodynamic equilibrium considerations. ln the preferred embodiment of the present invention, hydrogen is utilized in the isomerization reaction zone to minimize cracking and to maintain the surface of the catalyst in a carbon free condition. The quantity of hydrogen utilized will range from about.0.1 to about 10 mols or more ofr 10 hydrogen per mol of hydrocarlcn`V4 Hydrogen consumption is exceedingly small, in the range of from Aabout 30 to about cubic feet per barrel of hydrocarbon feed.

Various alkylcycloparain ring-opening catalysts are utilizable in the second reaction zone in the process of this invention. Ring-opening catalysts which are preferred for the present process contain metals of the iron group or their oxides. These catalysts and particularly those containing the metals, nickel and cobalt, are also active demethylation and hydrogenation catalysts. The different ring-opening catalysts comprising iron group metals or their oxides may be used as such but preferably they are supported on a carrier, such as alumina, silica, diatomaceous earth, crushed porcelain, or some other refractory material which has substantially no adverse influence on the ring-opening reaction of alkylcycloparalin. A highly active nickel catalyst which can be used in the present process contains approximately 66% by weight of total nickel, 30% of diatomaceous earth, and 4% of oxygen, the latter being present as nickel oxide. This catalyst is readily prepared by methods well known to those skilled in the art. In the continuous process of the present invention this catalyst is utilized las pellets or formed particles. These pellets or formed particles can be readily produced by mixing the powdered catalyst with graphite or some other lubricant prior to pilling thereof by a pilling machine. Other nickel-containing catalysts which may be employed similarly may be prepared to contain proportions of nickel different from those given above. The alkylcycloparafn ring-openinU catalyst is reduced with hydrogen prior to utilization thereof in this process. The reduction is carried out at a temperature of from about 700 F. to about 1200 F., and preferably at a temperature of about 800 F. to about 1100 F. in order to obtain a ring-opening catalyst of such activity that the ring-opening reaction can be controlled readily to produce isoparaflins from alkylcycloparafins. In place of nickel catalysts, cobalt catalysts may also be utilized in the alkylcycloparafn ring-opening step in the process of this invention. The methods of preparation of such cobalt catalysts are also well known to those skilled in the art.

The alkylcycloparan ring-opening reaction or step is carried out by contacting hydrogen and a portion of the isomerization reaction zone efuent with the herein-above stated catalyst at temperatures ranging from about 300 F. to about 750 F. and pressures of from about 25 to about 2000 pounds per square inch. The liquid hourly space velocities over these catalysts will range from about 0.1 to about 10 or more, the only limitation being that substantially all of the alkylcycloparaflins in thefeed to this reaction zone shall be converted to isoparans. The quantity of hydrogen utilized will range from about 0.5 to about 10 mols or more of hydrogen per mol of hydrocarbon feed to this reaction zone. Hydrogen consumption in this reaction zone will depend upon the amount of alkylcycloparathns converted, one mol of hydrogen being consumed per mol of alkylcycloparain converted to isoparaiiin.

The process of the present invention can perhaps be best understood by reference to the attached drawing which is a schematic diagram of the process ow.

Referring to the drawing, a saturated hydrocarbon fraction characterized by an average molecular weight greater than about 80, for example, a hexane fraction, separated from a Straight run or a catalytically reformed naphtha, is passed, as a liquid under pressure, through line l to a middle or upper portion of fractionation zone 2. The fresh feed to fractionation zo-ne 2 is fractionated therein to separate a substantially monomethyl and normal parafn free overhead from the net fresh feed to the isomerization reaction zone. Thus, the overhead comprises primarily, in the case of hexane, a dimethylparain stream. Separation of these dimethylparans at this point prevents reverse isomerization thereof and further allows isomerization of monomethyl and normal 11 parafhns to proceed to additional quantities of these dimethylparaffins. Thus, the net feed from line 1 is fractionated in fractionation zone 2 and the dimethylparafiin portion thereof is separated overhead. This overhead fraction passes through line 3, is condensed in condenser 4, and passed through line 5 to overhead receiver 6. Overhead receiver 6 is equipped with a vent line 7 containing a pressure control valve 8. By means of this vent line and pressure control valve, the small quantities of low boiling hydrocarbons present in the fresh feed can be vented, if desired, from the dimethylparatins in the overhead receiver. The net dimethylparaflin fraction is withdrawn from overhead receiver 6 through line 9 by means of pump 10 which discharges to line 11. A portion of the overhead is recycled through line 12 to the top of fractionation zone 2 as reliux therefor. The net dimethylparaflins in the fresh feed are withdrawn through line 13 as one product from the process. Fractionation zone 2 is heated by withdrawing a portion of the higher boiling bottoms from line 14 through line 17, .s

reboiler 18, and line 19. The desired quantity of heat s imparted to these hydrocarbons in reboiler 18.

The dimethylparaflin-free portion of the fresh feed is withdrawn from fractionation zone 2 through line 14 by pump 15. This net isomerization reaction zone feed then passes through lines 16 and 21 to heat exchange zone 22. On passage through line 21, this net fresh feed has combined therewith recycle from the ring-opening reaction zone hereinafter described. The combined feed is heat exchanged in heat exchange zone 22 with effluent from the isomerization reaction zone and passes through line 23 to heater 24 wherein any necessary additional heat is added. The thus heated combined feed is then passed from heater 24 through line 25, has hydrogen combined therewith from line 26 and passes through line 27 to isomerization zone 28.

Isomerization zone 28 is of the conventional type, preferably adiabatic, and is packed with a solid bed of isomerization catalyst as described hereinabove. ln this isomerization reaction zone the less highly branched chain and straight chain hydrocarbons are isomerized to an equilibrium mixture of paranic hydrocarbons. Furthermore, the naphthenic hydrocarbons are also isomerized to an equilibrium mixture thereof in the presence of this catalyst. The hydrogen which was introduced to this zone along with the combined feed hydrogenates any aromatic hydrocarbons introduced thereto from the fresh feed and thus produced naphthenic hydrocarbons are also isomerized to an equilibrium mixture of the sarne. useful function in that it tends to prevent the formation of sludge-like materials by hydrogenation thereof at or just after formation. Thus, the catalysts which are utilized in this zone can be utilized over long periods of time without the necessity for regeneration or removal thereof from this isomerization reaction zone.

The conditions utilized in isomerization reaction zone 28 will depend upon the particular isomerization catalyst used therein. As was pointed out above, a preferred catalyst in the process of this invention is one containing a platinum group metal, particularly platinum, alumina, and combined halogen. With such a catalyst, the pressure utilized in the reaction zone will range from about 100 to about 1000 pounds per square inch, the temperature will range from about 300 F. to about 825 F., and the hourly liquid space velocity will range from about 0.1 to about l0. The hydrogen to hydrocarbon ratio in the isomerization reaction zone will range from about 0.1 to about mols of hydrogen per mol of hydrocarbon. When the catalyst utilized comprises platinum, alumina, and lcombined fluorine, the latter in an amount of from about 2.5 to about 4.5% by weight, the reaction temperature will be lower than the higher part of the above set forth range, for example, from about 500 F. to about 750 F. When the catalyst The hydrogen also serves a further comprises platinum, alumina, with or without combined halogen, onto which has been impregnated a metal halide of the Friedel-Crafts type, such as aluminum chloride, the temperature will be still lower, for example, from about 300 F. to about 500 F. In some instances it may be desirable and/or advisable to utilize hydrogen halide along with these catalysts, and thus the use of hydrogen chloride, for example, along with these catalysts is within the generally broad scope of this invention.

The isomerization reaction zone effluent passes from reaction zone 23 through line 29 in indirect heat exchange with the reaction zone feed through heat exchanger 22 and then passes through line 30, is cooled in condenser 31, and passes through line 32 to high pressure separator 33. The high pressure separator 33 is utiiized for separating hydrogen, and low boiling cracked products, if any, from the reaction zone effluent. This hydrogen is separated and passed through line 34 containing pressure control valve 35. lf it is desired to recycle this hydrogen, pressure control valve 35 is closed and valve 37 is opened. The hydrogen then passes through lines 34, 36, and 39 to compressor 4t). Fresh hydrogen is added through line 38. lt is readily apparent that by varying the positions of valves 35 and 37, and by varying the quantity of fresh hydrogen, any or all of the hydrogen separated in high pressure separator 33 may be recycled. The hydrogen is compressed to the desired pressure by compressor 40 and discharged to line 26 hereinabove described.

The liquid reaction zone eliluent is withdrawn from high pressure separator 33 and is passed to a second fractionation zone 42. Fractionation zone 42 not only removes the desired -second product from the process but also is a feed preparation column for the preparation of thefeed to the alkylcycloparafn ring-opening reaction zone. Thus, the feed to this fractionation zone is fractionated therein and dimethyl and monomethylparaflins are separated overhead. The thus fractionated and separated overhead passes from fractionation zone 42 through line 43, is condensed in condenser 44, and passes through line 45 to overhead receiver 46. Overhead receiver 46 contains a vent line 47 and a pressure control valve 48 in this vent line. By means of this vent line and pressure control valve low boiling hydrocarbons, if any, may bc removed from the desired product. The net overhead comprising dimethylparaflins and monomethylparains produced in the isomerization reaction zone are withdrawn from overhead receiver 46 through line 49 by means of pump 50 which discharges through line 51. From line 5l a portion of the overhead product is passed to an upper section of fractionation zone 42 as reflux therefor. The net overhead product (and second product from the process) is withdrawn by means of line 53. In a still further embodiment of this invention, this second product of the process may be fractionated to produce a still higher octane number product and to sepa` rate a recycle stream therefrom. In this embodiment, for example, valve 81 is closed, valve 82 is changed from its normally closed position to an open position, and the second product from the process is directed from line 53 through lines 83 and 1 to fractionation zone 2. When the overhead product from fractionation zone 42 is a mixture o-f dimethylbutanes and monomethylpentanes, the dimethylbutanes will be fractionated overhead in fnactionation zone 2 to produce only the highest octane number product, and the monomethylpentanes will be recycled to the isomerization reaction zone for further conversion into higher octane number products. In this manner, dimethylbutanes can be made the only product from the process when the process is utilized for the conversion of a hexane hydrocarbon fraction. This fractionation of the :second product from the process can also be carried out in an independent zone not shown. Fractionation zone 42 is heated by withdrawing a portion of the higher boiling hydrocarbons through lines 54 and 56. These hydro- 'carbons are directed to ,and heated in reboiler 57 and then Vare passed by means of line 58 back to'fractionationzone 42 wherein heat is imparted to this zone.

The bottoms from fractionation zone 42 are withdrawn therefrom through line 54 by means of pump 55. These bottoms are the net alkylcycloparain ring-opening reaction zone feed. Pump 55 is the reaction zone feed pump by means of which the feed is passed through line 59 in indirect heat exchange with the reaction zone e'luent in heat exchanger 60. From this heat exchanger the feed then passes through line 61 ,to heater 62 wherein the necessary heat is imparted to these hydrocarbons. In heater 62 the temperature-of these hydrocarbons is raised to within the desired 300-750 F. and the hydrocarbons then pass through lines 63 and 65 to alkylcycloparaffin ring-opening reaction zone 66. Prior to their passage thereto they are joined with hydrogen from line 64. g

Alkylcycloparafn ring-opening reaction zone 66 is of the conventional type, preferably adiabatic, and is packed with alkylcycloparafn ring-opening catalyst described hereinabove. In this ring-opening reaction zone `the cycloparaffin rings of alkylcycloparains are opened by means of hydrogen. With reference to the total cycloparan or naphthene feed to this reaction zone, the reaction is specific in that unsubstituted cycloparafns do not react. Thus, for example, when the naphthenes present in this feed are methylcyclopentane and cyclohexane, the cyclohexane passes through this zone unconverted while the methylcyclopentane is converted into a mixture of 2- and 3-methylpentane. This is a hydrogen consuming reaction and one mole of hydrogen is consumed for each mole of `alkylcrycloparatn which is converted into branched chain paraiins. Therefore, not'only Vmust there be hydrogen charged to this reaction zone, but at least as much hydrogen should be charged as will be consumed mole for mole based on the alkylcycloparafns in the feed to the zone. At the higher temperatures within the above disclosed range utilizable in this zone,v some demethylation of` normal paraflns tends to take place. Thus, for example, a portion of the normal hexane in a -six carbon atom feed to this zone will be converted to'normal pentane and methane. The methane is separated from lthe liquid products as hereinafter described in the high pressure separator and the normal pentane is recycled to the isomerization reaction zone for conversion into an equilibrium mixture of isoand normal pentane. As stated hereinabove the hydrogen which is introduced 4to the zone acts as a reactant therein. The hydrogen also serves a further useful function in thatit tends to prevent the formation of coke on the catalyst by hydrogenation of any parafnic radicals formed therein. Thus, the catalysts which are utilized in this alkylcycloparafn ring-opening reaction -zone can be utilized over long periods of time withoutthe necessity for regeneration Vor removal thereof from this reaction zone.

The conditions utilized in the alkylcycloparain ringopening reaction zone will depend upon the particular catalyst used therein. As was pointed out hereinabove, ra preferred catalyst for use in this reaction zone in the process of this invention is one containing `about 66% nickel, about 30% diatomaceous earth, and about 4% oxygen, the latter being combined with the nickel as nickel oxide. With -such a catalyst, the pressure utilized in this zone will range from about 25 to about 2000 pounds per square inch. The temperature will range from about 300 F. to about 750 F., andthe hourly liquid space velocity Will range yfrom about 0.1 to about l0. The hydrogen to hydrocarbon ratio in the ring-opening reaction zone will range from about 0.5 to about moles or more of hydrogen per mole of hydrocarbon, the hydrogen to hydrocarbon ratio being limited,'of course, to a minimum value suicient to providey the necessary quantity of hydrogen consumed in the reaction.V

The alkylCYClOP-fn Ying-Opening reaction zone etllu- 14 ent passes from-reaction "zone-'66 through line 67 in vindirect heat exchange with reaction `zone feed through heat exchanger' 60 and then passes through line 68, is cooledin condenser 69, and passes through line 70 to high pressure separator 71. This high pressure separator 71. This high pressure separator 71 is utilized for separating hydrogen, and lowvboiling cracked products, par- Vticularly methane, if any, from the reaction zone effluent. This hydrogen is separated and passed through line 72 containing pressure control valve 73. If it is desired to recycle this hydrogen, pressure-control valve 73 is closed and valve 75 is opened. The hydrogen then passes through lines 72, '74,' and 77 to compressor 78. Fresh hydrogen is added through line 76., It is readily apparent that by varying, positions of valves 73 and 75, and by varying the quantity of fresh hydrogen, any or all of the hydrogen separated in'high pressure separator 71 may be recycled. The hydrogen is compressed to the desired pressure by compressor 78 and discharged to line 64 hereinabove described. K

The liquid alkylcycloparan ring-opening reaction zone effluent is withdrawn from high pressure separator 71 through line 79 by means of p ump 80. Pump 80 passes this liquid efuent through line 20 to the isomerization reaction'zonel Thus, pump 80` is a recycle pump and provides'means by which' the recycle part of the combined feed is furnished to the isomerization reaction zone. This invention is illustrated further by means of the following examples which are introduced solely for the purpose of illustration and with no intention of unduly limiting the generally broad scope of this invention.

- EXAMPLE I This example illustrates the process of the present in- Vention utilizing a platinum-alumina-aluminum chloride catalyst in the isomerization reaction zone, and a Vnickelkieselguhr'catalyst in the 'alkylcycloparaflin ring-opening reaction zone. The isomerization zone catalyst comprises alumina containing about 0.4% platinum having impregnated thereon about 5% by weight of aluminum chloride. The alkylcycloparain ring-opening zone catalyst comprises about 66% nickel, about 30% kieselguhr, and about 4% oxygen, the latter being combined with the nickelV as nickel oxide.

The hydrocarbon feed stock utilized in this example is a Gulf Coast hexane fraction, boiling point 104-165 F. The composition of this Gulf Coast hexane fraction is as follows: cyclopentane, 3%; 2,2-dimethylbutane, 3%; 2,3- dimethylbutane, 5%; 2-methylpentane, 25%; 3-methylpentane, 20%; normal hexane, 30%; methylcyclopentane, 4%; cyclohexane, 7%; and benzene, 3%. Referring again to the drawing, this hexane fraction, having an average molecular weight greater than'80, in the quantity of 1000 barrels per day, is passed as a liquid under pressure through line 1 to an upper portion of fractionation zone 2. This feed to fractionation zone 2 is fractionated therein under a 4:1 molal reux to feed ratio and a substantially monomethylpentane and normal hexane free stream is separated overhead therefrom in an amount of barrels per day. This 110 barrels per day contains 30 barrels per day ofcyclopentane, 30 barrels per day of 2,2-dimethylbutane, and 50 barrels per day of 2,3-dimethylbutane. This fractionator overhead is withdrawn from fractionation zone 2 through line 3, is condensed in condenser 4, and is passed through line 5 to receiver 6. From receiver 6 the'net product is withdrawn through line 9 by means of pump 10 and is passed through lines 11 and 13 to storage. This is the rst product from the process.

Fractionation zone 2 bottoms are withdrawn through line 14 by means of pump 15 in the quantity of 890 barrels per day. This 890 barrels per day contains 250 barrels per day of Z-methylpentane, 200 barrels per day of S-methylpentane, 300 barrels per day of normal hexane, 40 barrels per day of methylcyclopentane, 70 barrels per day of cyclohexane, and 30 barrels per day of benzene.

At the junction of lines 16 and 21 this bottoms hydrocarbon fraction has combined therewith 367 barrels per day of recycle. This 367 barrels per day of recycle contains 88.5 barrels per day of Z-methylpentane, 51.5 barrels per day of S-methylpentane, 157 barrels per day of normal hexane, and 70 barrels per day of cyclohexane. Summation of these two feed streams gives a combined feed to the isomerization reaction zone in the quantity of 1257 barrels per day at a combined feed ratio of 1.41. The combined feed contains 338.5 barrels per day of 2- methylpentane, 251.5 barrels per `day of B-methylpentane, 457 barrels per day of normal hexane, 40 barrels per day of methylcyclopentane, 140 barrels per day of cyclohexane, and 30 barrels per day of benzene. This combined feed passes through line 21, through heat exchanger 22 in indirect heat exchange with the reaction zone effluent, and then through line 23 to heater 24. In heater 24 this combined feed has sufficient heat imparted thereto to raise its temperature to 340 F., the temperature of reaction in isomerization reaction zone 28. From heater 24 the combined feed then passes through line 25, has added thereto hydrogen from line 26 in a quantity to provide a hydrogen to hydrocarbon ratio of 1:1, and is passed through line 27 to isomerization reaction zone 28. The reaction in this zone is carried out at a pressure of 500 p.s.i.g. in vapor phase at a liquid hourly space velocity of 2.0. As set forth hereinabove, isomerization of the combined feed is accomplished in reaction Zone 28 in the presence of the hereinabove described isomerization reaction zone catalyst and this isomerization results in the production of 1257 barrels per day of reaction zone effluent containing 218` barrels per day of 2,2-dimethylbutane, 109 barrels per day of 2,3-dimethylbutane, 356 barrels per day of 2- methylpentane, 207 barrels per day of 3-methylpentane, 157 barrels per day of normal hexane, 140 barrels per day of methylcyclopentane,v and 70 barrels per day of cyclohexane. The benzene which was present in the combined feed was hydrogenated to cyclohexane which in turn was converted into an equilibrium mixture of cyclohexane and methylcyclopentane at the specified conditions. o

The reaction zone effluent after heat exchange with the incoming reaction zone feed is passed via lines 29 and 30 to condenser 31, and the liquid product and hydrogen gas are then passed through line 32 to high pressure separator 33. The hydrogen gas and minor amounts of low boiling hydrocarbons formed by cracking in the reaction zone are separatedV in high pressure separator 33 and are passed through lines 34, 36 and 39l to compressor 40. The liquid hydrocarbon isomerization reaction Zone eluent is passed from separator 33 through line 41 to fractionation zone 42. In fractionation zone 42 the dimethylbutanes and monomethylpentanes are fractionated from normal hexane and higher boiling hydrocarbons. Fractionation zone 42 is of the conventional type equipped with trays, packing, etc., as may be desired. The net liquid isomerization reaction zone effluent in the quantity of 1257 barrels per day is fractionated therein under a 4:1 molal reux to feed ratio and the overhead is passed therefrom through line 43, is condensed in condenser 44, and is passed through line 45 to overhead receiver 46. This overhead in the quantity of 890 barrels per day contains 218 barrels per day of 2,2-dimethylbutane, 109 barrels per day of 2,3-dimethylbutane, 357 barrels per day of 2-methylpentane, and 207 barrels per day of 3- methylpentane. The net overhead is withdrawn from' receiver 46 through line 4 9 by means of pump 50 and is passed through lines 51 and 53 to storage not shown. This overhead comprises the second product from the process. o y

The bottoms from this fractionation zone 4 2 are Withdrawn through line 54 by meansof pump 55 in the quantity of 367 barrels per day. This 367 barrels per day contains 157 barrels per day of normal hexane, 140 barrels per day of methylcyclopentane, and 70 barrels per day of l.. cyclohexane. These hydrocarbons are passed by means of pump 55 through line 59 in indirect heat exchange with reaction zone efluent inheat exchanger 60 and are passed through line 61 to heater'l 62. In heater 62 the necessary amount of heat for reaction zone 66 is imparted to these hydrocarbons. The hydrocarbons are withdrawn from heater 62 at a temperature of 600 F. and are passed through lines 63 and 65 to alkylcycloparafn ring-opening reaction zone 66. Prior to passage thereto they have combined therewith hydrogen such that the hydrogen to hydrocarbon mole ratio is 1:1. In reaction zone 66 the alkylcycloparaflin rings of the methylcyclopentane are opened and this compound is converted into a mixture of A2- and 3-rnethylpentane. This reaction is carried out at a temperature of 500 F., a pressure of 350 pounds per square inch, in vapor phase at a liquid hourly space velocity of about 1.0. The resulting reaction zone eluent in the quantity of 367 barrels per day is withdrawn from reaction zone 66, heat exchanged with fresh feed to this zone, and passed through lines 67 and 68, condensed in condenser 69, and passed through line 70 to high pressure separator 71. This 367 barrels per day of effluent contains 88.5 barrels per day of Z-methylpentane, 51.5 barrels per day of 3methylpentane, 157 barrels per day of normal hexane, and 70 barrels per day of cyclohexane. In high pressure separator 71 the hydrogen is removed and passes through lines 72, 74 and 77 to compressor 78. The liquid effluent is Withdrawn through line 79 by pump 80 and is passed through line 20 for combination with the net fresh feed to provide the combined feed for the isomerization reaction zone.

EXAMPLE II This example illustrates the process of the present invention in utilizing a platinum-alumina-combined halogen catalyst in the isomerization reaction zone, and nickelkieselguhr catalyst in the alkylcycloparafn ring-opening reaction zone. The isomerization zone catalyst comprises alumina containing about 0.4% platinum and about 4.0% combined tluorine. The alkylcycloparatiin ring-opening zone catalyst comprises about 66% nickel, about 30% kieselguhr, and about 4% oxygen, the latter being combined with the nickel as nickel oxide.

The hydrocarbon feed stock utilized in this example is the same Gulf Coast hexane fraction described hereinabove in Example I. Referring again to the drawing, this hexane fraction having an average molecular weight greater than 80, in the quantity of 1000 barrels per day is passed as a liquid under pressure through line 1 to an upper portion of fractionation zone 2. This feed to fractionation zone 2 is fractionated therein under a 4:1 molal reflux to feed ratio, and a substantially monomethylpentane and normal hexane free stream is separated overhead therefrom in an amount of barrels per day. This 110 barrels per day contains 30 barrels per day of cyclopentane, 30 barrels per day of 2,2-dimethylbutane, and 50 barrels per day of 2,3-dimethylbutane. This fractionator overhead is withdrawn from fractionation zone 2 through line 3, is condensed in condenser 4, and is passed through line 5 to receiver 6. From receiver 6 the net product is withdrawn through line 9 by means of pump 10 and is passed through lines 11 and 13 to storage. This is the first product from the process. y

Fractionation zone 2 bottoms are Withdrawn through line 14 by means of pump 15 in the quantity of 890 barrels per day. This 890 barrels per day contains 250 barrels per day 0f 2-methylpentane, 200 barrels per day of S-methylpentane, 300 barrels per day of normal hexane, 40 barrels per day of methylcyclopentane, 70 barrels per day of cyclohexane, and 30 barrels per day of benzene. At the junction of lines 16 and 21 this bottoms hydrocarbon fraction has combined therewith 430 barrels per day of recycle containing 84.6 barrels per day of Z-methylpentane, 55.4 barrels per day of B-methylpentane, 276 barrelsper day of normal hexane, and 14 barrels per day ofcyclohexane. Summation of the'setWo feed streams gives a combined feed tothe isomerization reaction zone in the quantity of 1320 barrels per day at a combined feed ratio of 1.48. The combined feed contains 334.6 barrels per day of 2methylpentane, 255.4 barrels per day of S-m'ethylpentane, 576 barrels per day of normal hexane, 40 barrels per day of methylcyclopentane, 84 barrels per day of cyclohexane, and 30 barrels per day of benzene. This combined feed passes through line 21, through heat exchanger 22 in indirect heat exchange with the reaction zone effluent, and then through line 23 to heater 24. In heater 24 this combined feed has sulicient heat imparted thereto to raise its temperature to 650 F., the temperature of reaction in isomerization reaction zone 28. From heater 24 the combined feed then passes through line 25, has added thereto hydrogen from line 26 in a quantity to provide a hydrogen to hydrocarbon ratio of 0.5 z 1, and it is passed through line 27 to isomerization reaction zone 28. The reaction in this zone is carried out at a pressure of 500 p.s.i.g. in vapor phase at a liquid hourly space velocity of 2.0. As set forth hereinabove, isomerization of the combined feed is accomplished in reaction zone 28 in the presence of the hereinabove described isomerization reaction zone catalyst and this isomerization results in the production of 1320 barrels per day of reaction zone effluent containing 139 barrels per day of 2,2-dimethylbutane, 91 barrels per day of 2,3-dimethylbutane, 398 barrels per day of 2methylpentane, 262 barrels per day of S-methylpentane, 276 barrels per day of normal hex ane, 140 barrels per day of methylcyclopentane, and 14 barrels per day of cyclohexane. The benzene which Was present in the combined feed was hydrogenated to cyclohexane which4 in turn was converted into an equilibrium mixture of cyclohexane and methylcyclopentane at the specified conditions. f

The reaction zone effluent after heat exchange with the incoming reaction zone feed is passed, via lines 29 and 30, to condenser 31, and the liquid product and hydrogen gas are then passed through line 32 to high pressure separator 33. The hydrogen gas and minor amounts of low boiling hydrocarbons formed by cracking in the reaction zone are separated in highpressure separator 33 and are passed through lines 34, 36, and 39 to compressor 40. The liquid hydrocarbon isomerization reaction zone efuent is passed from separator 33 through line 41 to fractionation zone 42. In fractionation zone 42 the dimethylbutanes and monomethylpentanes are fractionated from normal hexane and higher boiling hydrocarbons. Fractionation. zone 42 is of the conventional type equipped with trays, packing, etc., as may be desired. The net liquid isomerization reaction zone effluent in the quantity of V1320 barrels per day is fractionated therein under a 4:1 molal reflux to feed ratio and the overhead is passed therefrom through line 43, is condensed in condenser 44, and is passed through line 45 to overhead receiver 46. This overhead in the quantity of 890 barrels per day contains 139 barrels per day of 2,2-dimethylbutane, 91 barrels per day of 2,3-dimethylbutane, 398 barrels per day of 2methylpentane, and 262 barrels per day of 3-methylpentane. The net overhead is Withdrawn from receiver 46 through line 49 by means of pump 50and passed through lines 51 and 53 to storage not shown. ThisV overhead comprises the second product from the process.

The bottoms from this fractionation zone 42 are withdrawn through line 54 by means of pump 55 in the quantity of 430v barrels per day. This 430 barrels per day contains 276 barrels per day of normal hexane, 140 barrels per day of methylcyclopentane and 14 barrels per day of cyclohexane. These hydrocarbons are passed, by means of Vpump 55, through line 59 and in indirect heat exchange with reaction zone effluent in heat exchanger 60 and are passed through line 61 to heater 62. In heater 62 the necessary amount of heat for reaction zone 66 is imparted to these hydrocarbons. The hydrocarbons are withdrawn from heater 62 at a temperature of 500 F. and are passed through line 63 and 65 to alkylcycloparaiin ring-opening reaction zone 66. Prior to passage thereto they have combined therein hydrogen such that the hydrogen to hydrocarbon mole ratio is 2:1. In reaction zone 66 the alkylcycloparain rings of the methylcyclopentane are opened and this compound is converted into a mixture of 2- and 3-methylpentane. This reaction is carried out at a temperature of 700 F., a pressure of about 200 pounds per square inch in vapor phase at a liquid hourly space velocity of about 0.5. The resulting reaction zone efuent in the quantity of 430 barrels per day is Withdrawn from reaction zone 66, heat exchanged with fresh feed to this zone, and passed through lines 67 and 68, condensed in condenser 69, and passed through line '70 to high pressure separator 71. This 430 barrels per day of effluent contains 84.6 barrels per day of 2methylpentane, 55.4 barrels per day of 3- methylpentane, 276 barrels per day of normal hexane and 14 barrels per day of cyclohexane. In high pressure separator 71 the hydrogen is removed and passes through lines 72, 74, and 77 to compressor 78. The liquid effluent is withdrawn through line 79 by pump 80 and is passed through line 20 for combination with the net fresh feed to provide the combined feed for the isomerization reaction zone.

I claim as my invention:

l. A process for the isomerization of an isomerizable saturated hydrocarbon fraction characterized by an average molecular Weight greater than about 80, and containing monomethyl, normal, and cycloparaliins, which comprises passing said fraction in combination with recycle produced as hereinafter described to an isomerization reaction zone containing an isomerization catalyst and therein isomerizing said fraction and recycle to a mixture of isomers thereof, fractionating the isomerization zone eiuent to produce an overhead fraction rich in dimethyland monomethylparaffins and a bottoms fraction rich in normal, and cycloparaflins, removing said overhead fraction as a product of the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparaflin ring-opening catalyst and therein opening the rings of alkylcycloparafns in the feed to said Zone, and passing the efuent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

2. A process for the isomerization of an isomerizable hexane hydrocarbon fraction containing monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, which comprises passing said fraction and hydrogen in combination with recycle produced as hereinafter described to an isomerization reaction zone. containing isomerization catalyst and therein somcrizing said fraction and recycle in the presence of hydrogen to a mixture of isomers thereof, fractionating the isomerization zone effluent to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as a product of the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparaffin ringopening catalyst and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen, and passing the effluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

3. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising a platinum group metal and a refractory metal oxide which comprises passing said hydrocarbon fraction to a first fractionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing at isomerization conditions in the presence of hydrogen said fraction and recycle to a mixture of isomers thereof, passing the isomerization zone eluent to a second fractionation zone, fractonating said eflluent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparaiiin ringopening catalyst comprising an iron group metal and therein opening the rings of the methylcyclopentane in the feed to said Zone by means of hydrogen, and passing the effluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

4. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomeri- Zation catalyst comprising platinum and alumina, which comprises passing said hydrocarbon fraction to a first fractionation Zone, fractonating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomeri- Zation catalyst and therein isomerizing at isomerization conditions in the presence of hydrogen said fraction and recycle to a mixture of isomers thereof, passing the isomerization zone eflluent to a second fractionation zone, fractonating said efuent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparafin ring-opening catalyst comprising metallic nickel and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen, and passing the efuent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

5. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising platinum and alumina having irnpregnated thereon a Friedel-Crafts metal halide, which comprises passing said hydrocarbon fraction to a first fractionation zone, fractonating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing at isomerization conditions inthe presence of hydrogen said fraction and recycle to a mixture of isomers thereof, passing the isomerization zone eiuent to a second fractionation zone, fractionating said eflluent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction Zone containing an alkylcycloparafiin ring-opening catalyst comprising metallic nickel and therein opening the rings of the methyl cyclopentane in the feed to said zone by means of hydrogen, and passing the effluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

6. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carriedoutin the presence of hydrogen and an isomerization catalyst comprising platinum, alumina, and combined halogen, which comprises passing said hydrocarbon fraction to a rst fractionation Zone, fractonating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing at isomerization conditions in the presence of hydrogen said fraction and recycle to a mixture of isomers thereof, passing the isomerization zone efuent to a second fractionation zone, fractonating said eflluent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparafin ring-opening catalyst comprising metallic nickel and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen, and passing the eluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

7. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising platinum, alumina, and combined halogen having impregnated thereon a Friedel-Crafts metal halide, which comprises passing said hydrocarbon fraction to a first fractionation zone, fractonating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing at isomerization conditions in the presence of hydrogen said fraction and recycle to a mixture of isomers thereof, passing the isomerization zone effluent to a second fractionation zone, fractonating said effluent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparan ring-opening catalyst comprising metallic nickel and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen, and passing the effluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

8. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina and from about 0.01% to about 2% by weight thereof of platinum, which comprises passing said hydrocarbon fraction to a lirst fractionation zone, fractonating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing Said overhead fraction as one product from the process.

passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 300 F. to about 825 F., a pressure of from about 100 to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, passing the isomerization zone effluent to a second fractionation zone, fractionating said eiuent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparaffin ring-opening catalyst comprising metallic nickel and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, and passing the effluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

9. AV process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina and from about 0.01% to about 2% by Weight thereof of platinum, which comprises passing said hydrocarbon fraction to a first fractionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced ashereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 300 F. to about 825 F., a pressure of from about 100 to about 1000 pounds per square inch, and a liquid hourly space velocity of from about0.1 to about 10, passing the isomerization zone effluent to a second fractionation zone, fractionating said efiiuent in said zone to produce an overhead fractionrich in dimethylbutanes and monomethylpentanes anda bottoms fraction rich innormal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing the bottoms fraction to a second reaction Yzone containing an alkylcycloparaftin ring-opening catalyst comprising about 66% nickel, about 30% diatomaceous earth, and about 4% oxygen, the latter being combined with nickel as nickel oxide, and therein opening the krings of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of fromabout 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and a liquid hourly space Velocity of from about 0.1 to about 10, and passingV the eliiuent from said second reaction zone toV the' isomerization reaction zone as aforesaid as recycle therefor.

10. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina, from about 0.01% to about 2% by weight thereof of platinum, and from about 0.1% to about 8% by Weight thereof of combined halogen, which comprises passing said hydrocarbon fraction to a first fractionation zone, fractionating saidV hydrocarbons to produce an overhead` fraction rich in dimethylbutanes and a bottoms fraction rieh'in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 300 F. to about 825 F., a pressure of from about 100 to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about l0, passing the isomerization zone effluent to a second fractionation zone, fractionating said effluent in said zone to produce on overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparan ring-opening catalyst comprising metallic nickel and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, and passing the eiluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

11. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina, from about 0.01% to about 2% by Weight thereof of platinum, and from about 0.3% to about 0.7% by weight'thereof of a mixture of combined fluorine and combined chlorine, which comprises passing said hydrocarbon fraction to a first fractionation zone, fractionating said hydrocarbons to produce on overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reac-tion zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 750 F. to about 825 F,. a pressure of from about to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about l0, passing the isomerization zone efliuent to a second fractionation zone, fractionating said efliuent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparatiin ring-opening catalyst comprising metallic nickel and therein opening the rings of the methylcylopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and a liquid hourly space velocity of fromlabout 0.1 to about 10, and passing the effluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

12. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina, from about 0.01% to about 2% by Weight thereof of platinum, and from about 0.3% to about 0.7% by Weight thereof of a mixture of combined iiuorine and combined chlorine, which comprises passing said hydrocarbon fraction to a first frac tionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 750 F. to about 825 F., a pressure of from about 100 to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, passing the isomerization zone eluent to a second fractionation zone, fractionating said efuent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing the bottoms fraction to a second reaction zone containing an alkylcycloparain ring-opening catalyst comprising about 66% nickel, about 30% diatomaceous earth, and about 4% oxygen, the latter being combined with nickel as nickel oxide, and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, and passing the eflluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

13. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina, from about 0.01% to about 2% by weight thereof of platinum, and from about 2.5% to about 4.5% by weight thereof of combined uorine, which comprises passing said hydrocarbon fraction to a first fractionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 500 F. to about 750 F., a pressure of from about 100 to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, passing the isomerization zone etfluent to a second fractionation zone, fractionating said efuent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparafn ring-opening catalyst comprising metallic nickel and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 7 50 F., a pressure of from about 25 to -about 2000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, and passing the effluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

14. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the pres-ence of hydrogen and an isomerization catalyst comprising alumina, from about 0.01% to about 2% by weight thereof of platinum, and from about 2.5 to about 4.5% by weight thereof of combined fluorine, which comprises passing said hydrocarbon fraction to a iist fractionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 500 F. to about 750 F., a pressure of from about 100 to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, passing the isomerization zone effluent to a second fractionation zone, fractionating said effluent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparain ring-opening catalyst comprising about 66% nickel, about 30% diatomaceous earth, and about 4% oxygen, the latter being combined with nickel as nickel oxide, and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, and passing the elfluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

15. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina and from about 0.01 to about 2% by weight thereof of platinum having impregnated thereon from about 2% to about 20% by weight thereof of a Friedel-Crafts metal halide, which comprises passing said hydrocarbon fraction to a first fractionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 300 F. to about 500 F., a pressure of from about 100 to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, passing the isomerization zone effluent to a second fractionation zone, fractionating said eluent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said ovehead as the second product from the process, passing said bottoms fraction to a. second reaction zone containing an alkylcycloparaflin ring-opening catalyst comprising metallic nickel and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, and passing the etuent from said 25 second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

16. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina and from about 0.01% to about 2% by Weight thereof of platinum having impregnated thereon from about 2% to about 20% by Weight thereof of aluminum chloride, which comprises passing7 said hydrocarbon fraction to a first fractionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination With recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 300 F. to about 500 F., a pressure of from about 100 to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, passing the isomerization zone effluent to a second fractionation zone, fractionating said efluent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparatiin ring-opening catalyst comprising metallic nickel and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and an hourly liquid space Velocity of from about 0.1 to about 10, and passing the effluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

17. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina and from about 0.01% to about 2% by Weight thereof platinum having impregnated thereon from about 2% to about 20% by Weight thereof of aluminum chloride, which comprises passing said hydrocarbon fraction to a first fractionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said ovehead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof Vsaid fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 100 to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, passing the isomerization zone eluent to a second fractionation zone, fractionating said eluent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparaiiin ring-opening catalyst comprising about 66% nickel, about 30% diatomaceous earth, and about 4% oxygen, the latter being combined with nickel as nickel oxide, and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, and passing the effluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

18. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina, from about 0.01% to about 2% by weight thereof of platinum, and from about 0.1% to about 8% by Weight thereof of combined halogen, having impregnated thereon from about 2% to about 20% by weight of a Friedel-Crafts metal halide, which comprises passing said hydrocarbon fraction to a first fractionation zone, fractionating said hydrocarbons to produce an ofverhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 300 F. to about 500 F., a pressure of from about to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, passing the isomerization zone eluent to a second fractionation zone, fractionating said etlluent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparafn ring-opening catalyst comprising metallic nickel and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, and passing the effluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

19. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina, from about 0.01% to about 2% by weight thereof of platinum, and from about 0.1% to about 8% by Weight thereof of combined halogen, having impregnated thereon from about 2% to about 20% by Weight thereof of aluminum chloride, which comprises passing said hydrocarbon fraction to a rst fractionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 300 F. to about 500 F., a pressure of from about 100 to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, passing the isomerization zone eiuent to a` second fractionation zone, fractionating said effluent in said zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparan ring-opening catalyst comprising metallic nickel and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and an hourly liquid space velocity of from about 0.1 to about 10, and passing the effluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

20. A process for the isomerization of an isomerizable hexane hydrocarbon fraction, said isomerization being carried out in the presence of hydrogen and an isomerization catalyst comprising alumina, from about 0.01% to about 2% by weight thereof of platinum, and from about 0.1% to about 8% by Weight thereof of combined halogen, having impregnated thereon from about 2% to about 20% by weight of aluminum chloride, which comprises passing said hydrocarbon fraction to a first fractionation zone, fractionating said hydrocarbons to produce an overhead fraction rich in dimethylbutanes and a bottoms fraction rich in monomethylpentanes, normal hexane, methylcyclopentane, and cyclohexane, removing said overhead fraction as one product from the process, passing said bottoms fraction in combination with recycle produced as hereinafter described and hydrogen to an isomerization reaction zone containing said isomerization catalyst and therein isomerizing to a mixture of isomers thereof said fraction and recycle in the presence of hydrogen at isomerization conditions including a temperature of from about 300 F. to about 500 F., a pressure of from about 100 to about 1000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, passing the isomerization Zone effluent to a second fractionation zone, fractionating said eluent in said Zone to produce an overhead fraction rich in dimethylbutanes and monomethylpentanes and a bottoms fraction rich in normal hexane, methylcyclopentane, and cyclohexane, removing said overhead as the second product from the process, passing said bottoms fraction to a second reaction zone containing an alkylcycloparafn ring-opening catalyst comprising about 66% nickel, about `30% diatomaceous earth, and about 4% oxygen, the latter being combined with nickel as nickel oxide, and therein opening the rings of the methylcyclopentane in the feed to said zone by means of hydrogen at a temperature of from about 300 F. to about 750 F., a pressure of from about 25 to about 2000 pounds per square inch, and a liquid hourly space velocity of from about 0.1 to about 10, and passing the eluent from said second reaction zone to the isomerization reaction zone as aforesaid as recycle therefor.

References Cited in the file of this patent UNITED STATES PATENTS 2,348,557 Mattox May 9, 1944 2,428,692 Voorhies Oct. 7, 1947 2,461,545 Hepp Feb. 15, 1949 2,766,302 Elkins Oct. 9, 1956 2,831,908 Starnes et al. Apr, 22, 1958 

2. A PROCESS FOR THE ISOMERIZATION OF AN ISOMERIZABL HEXANE HYDROCARBON FRACTION CONTAINING MONOMETHYLPEN TANES, NORMAL HEXANE, METHYLCYCLOPENTANE, AND CYCLOHEX ANE, WHICH COMPRISES PASSING SAID FRACTION AND HYDROGE IN COMBINATION WITH RECYLE PRODUCED AS HEREINAFTER DE SCRIBED TO AN ISOMERIZATION REACTION ZONE CONTAINING ISOM ERIZATION CATALYST AND THEREIN ISOMERIZING SAID FRACTION AND RECYLE IN THE PRESENCE OF HYDROGEN TO A MIXTURE OF ISOMERS THEREOF, FRACTIONATING THE ISOMERIZATION ZONE EFFLUENT TO PRODUCE AN OVERHEAD FRACTION RICH IN DIMETHYLBUTANES AND MONOMETHYLPENTANES AND A BOTTOMS FRACTION RICH IN NORMAL HEXANE, METHYLCYCLOPENTANCE, AND CYCLOHEXANE, REMOVING SAID OVERHEAD FRACTION AS A PRODUCT OF THE PROCESS, PASSING SAID BOTTOMS FRACTION TO A SECOND REACTION ZONE CONTAINING AN ALKYLCYCLOPARAFFIN RINGOPENING CATALYST AND THEREIN OPENING THE RINGS OF THE METHYLCYCLOPENTANE IN THE FEED TO SAID ZONE BY MEANS OF HYDROGEN, AND PASSING THE EFFLUENT FROM SAID SECOND REACTION ZONE TO THE ISOMERIZATION REACTION ZONE AS AFORESAID AS RECYCLE THEREFOR. 